我强颜欢笑换你一世倾城
[wŏ qiáng yán huān xiào huàn nĭ yī shì qīng chéng]
A poetic expression where 'I force a smile for your lifetime enchantment'; it reflects a profound love and selfless dedication even if not fully returned, choosing happiness by pretending to be cheerful just because the other person exists.